Field of the Invention
The present invention relates to an electronic apparatus and method that are capable of supplying power to a control unit and charging a battery using power supplied from an external apparatus.
Description of the Related Art
A system that supplies power supplied from an external apparatus to a system load (corresponding to an electrical load of a system) and a battery is known (Japanese Patent Laid-Open No. 2013-59206).
Incidentally, in Japanese Patent Laid-Open No. 2013-59206, in a case where in a battery-operated state (a state where the system load operates with power supply from the battery), a disadvantage is conceivable that the voltage supplied to the system load decreases due to the influence of a switch circuit connected between the system load and the battery. In addition, in the battery-operated state, another disadvantage is also conceivable that power loss occurs due to the switch circuit connected between the system load and the battery.
However, these disadvantages are not considered in Japanese Patent Laid-Open No. 2013-59206. Consider the case where the switch circuit includes a MOSFET (metal-oxide-semiconductor field-effect transistor), for example. In this case, if the battery-operated state is started when power is not supplied from an external apparatus and then a large current flows through the switch circuit, on-resistance occurs between a drain and a source, and a decrease in the voltage supplied to the system load and power loss due to the switch circuit occur. As a result, operations of the system load may possibly become instable, and the remaining capacity and the operable time of the battery decrease. In particular, in a case where the battery voltage is low, the on-resistance further increases since the gate voltage decreases. As a result, the voltage supplied to the system load further decreases, and power loss due to the switch circuit further increases. In this case as well, operations of the system load may possibly become instable, and the remaining capacity and the operable time of the battery decrease.